U.S. patent application number 10/362929 was filed with the patent office on 2003-10-09 for method and device for detecting a given material in an object using electromagnetic rays.
Invention is credited to Beneke, Knut, Meder, Claus, Naumann, Dirk, Nittikowski, Joerg, Ries, Hermann, Siedenburg, Uwe, Ullrich, Stefan.
Application Number | 20030190011 10/362929 |
Document ID | / |
Family ID | 7701568 |
Filed Date | 2003-10-09 |
United States Patent
Application |
20030190011 |
Kind Code |
A1 |
Beneke, Knut ; et
al. |
October 9, 2003 |
Method and device for detecting a given material in an object using
electromagnetic rays
Abstract
A method for the detection of a specific material in an object
(1), especially in a piece of luggage, using electromagnetic beams,
whereby the intensities of non-absorbed beams from at least three
beam planes (5.1-5.2) in corresponding detector arrays (4.1-4.5)
are measured and evaluated, using the following steps according to
the invention: 1. generating an at least two-dimensional picture of
the object (1) from the measured intensity values; 2. selecting one
of the spatial regions displayed in the picture as a basis of the
value of a material value, which is determined from intensity
measurements, for examination; 3. determining at least one
spatial-geometric value in the region to the examined from
positional data of a two-dimensional picture and from intensity
values using a stored value of a specific, absorption-influenced
value of a suspected material. 4. determining, in addition, the
corresponding spatial-geometric value solely from three-dimensional
geometric values, which are determined from measured intensity
values; and 5. comparing, directly or indirectly, values of the
spatial-geometric values determined in steps 3 and 4, or values
derived therefrom, in order to determine if the suspected material
is actually present.
Inventors: |
Beneke, Knut; (Ober-Olm,
DE) ; Nittikowski, Joerg; (Hohenstein-Holzhausen,
DE) ; Naumann, Dirk; (Lorsch, DE) ; Ries,
Hermann; (Taunusstein, DE) ; Siedenburg, Uwe;
(Essenheim, DE) ; Meder, Claus; (Rossdorf, DE)
; Ullrich, Stefan; (Saarbruecken-Klarenthal, DE) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
7701568 |
Appl. No.: |
10/362929 |
Filed: |
February 27, 2003 |
PCT Filed: |
September 21, 2002 |
PCT NO: |
PCT/EP02/10629 |
Current U.S.
Class: |
378/57 |
Current CPC
Class: |
G01V 5/0016
20130101 |
Class at
Publication: |
378/57 |
International
Class: |
G01N 023/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 5, 2001 |
DE |
101 49 254.5 |
Claims
1. Method for detecting a specific material in an object (1),
especially in a piece of luggage, using electromagnetic beams,
whereby the intensities of non-absorbed beams from at least three
beam planes (5.1-5.2) in corresponding detector arrays (4.1-4.5)
are measured and evaluated, using the following method steps: 1.
generating an at least two-dimensional picture of the object (1)
from the measured intensity values; 2. selecting one of the spatial
regions displayed in the picture as a basis of the value of a
material value, which is determined from intensity measurements,
for examination; 3. determining at least one spatial-geometric
value in the region to the examined from positional data of a
two-dimensional picture and from intensity values using a stored
value of a specific, absorption-influenced value of a suspected
material. 4. determining, in addition, the corresponding
spatial-geometric value solely from three-dimensional geometric
values, which are determined from measured intensity values; 5.
comparing, directly or indirectly, values of the spatial-geometric
values determined in steps 3 and 4, or values derived therefrom, in
order to determine if the suspected material is actually
present.
2. The method of claim 1, characterized in that an indirect
comparison is executed in such a way that by using both values of
the spatial-geometric values of steps 3 and 4, the value of a
specific material value is calculated, which subsequently is
compared with a stored value.
3. The method of claim 1 or 2, characterized in that in step 3, the
area of the image of the region to be examined is calculated, and
the volume of the material in the region of the area and the
absorption thickness of the region is subsequently determined as a
spatial-geometric value, whereby the absorption thickness is
determined from measured intensity values and the stored value of
the specific, absorption-influenced value of a suspected material;
in step 4, the approximate volume of the material of the region is
determined from spatial positional data, which are determined from
intensity values of at least three detector arrays (4.1-4.5).
4. The method of claim 3, characterized in that in step 5, the
values of the volume or the values of a value calculated with a
volume are compared with one another.
5. The method of claim 4, characterized in that the mass values are
compared with one another, which were calculated through
multiplying the volume values with the density value, which was
stored or determined from the stored value.
6. The method of claim 3, characterized in that in step 3, as a
final step, the mass of the material in the region is calculated
with the volume of the material and the stored density, and in step
5, for an indirect comparison, the density of the mass determined
in step 3 and the volume determined in step 4 is calculated and
compared with the stored density value.
7. The method of one of claims 3-6, characterized in that for the
approximation of the volume in step 4 the volume of a Polyhedron,
either located in the region or encompassing the region, is
calculated from positional data, which is derived from intensity
values of at least three detector arrays.
8. The method of claim 1, characterized in that in step 3, an
absorption thickness of the region corresponding to a position of
the two-dimensional picture, utilizing a stored value of the
specific, the absorption-influenced value of a suspected material
is determined; in step 4, the corresponding thickness of the region
is determined from spatial positional data, which was derived
solely from intensity values of at least 3 detector arrays
(4.1-4.5); and in step 5, the two determined thicknesses, or values
derived therefrom, are compared to one another.
9. The method of one of claims 1-7, characterized in that the
material value in the selection in step 2 is based on is the
effective atomic number Z.sub.eff.
10. The method of one of claims 1-9, characterized in that the
stored material-specific, absorption-influenced value in step 3 is
density .phi. and/or mass attenuation coefficient .mu./.phi..
11. The method of one of claims 1-10, characterized in that the
object (1) is radiated in at least three separate beam planes
(5.1-5.5), at least two of which are not parallel to one
another.
12. The method of claim 11, characterized in that the object (1) is
transported through the beam planes (5.1-5.5) for radiation.
13. A device for the application of one of the methods of one of
claims 1-12, comprising a transport means (7) moving through a
radiation tunnel (6) and radiation sources (3.1-3.3) positioned
around the transport means, said radiation sources emitting beams
in at least three beam planes (5.1-5.5) each aligned with a
corresponding detector (4.1-4.5), characterized in that at least
two of the beam planes (5.1-5.5) are not parallel with one another.
Description
TECHNICAL FIELD
[0001] The invention relates to a method and a device for detecting
a specific material in an object, especially in a piece of luggage,
using electromagnetic beams, whereby the intensities of
non-absorbed beams from at least three beam planes in corresponding
detector arrays are measured and evaluated.
[0002] In conventional methods and devices for the inspection of
objects, e.g., security screening of luggage at airports, the
object is transported by electromagnetic rays, which radiate from
stationary radiation sources. The intensities of the non-absorbed
beams are measured and evaluated by the corresponding detector
arrays assigned to the radiation sources. Generally, x-rays are
used for the inspection.
CONVENTIONAL ART
[0003] U.S. Pat. No. 6,088,423-A discloses a method whereby three
stationary radiation sources give forth x-rays in three planes
parallel to one another, which run vertically to the travel
direction. From the data of the three corresponding detector
arrays, a computer determines possible contours of the articles in
the object and calculates for each article an estimated effective
atomic number Z.sub.eff and an estimated density. In this manner,
the intensities of two energy ranges are evaluated, via the known
dual-energy-method.
EMBODIMENT OF THE INVENTION
[0004] It is an object of the invention to provide a method for
detection of materials in an object, especially in a piece of
luggage, which offers the highest possible security in the
detection of materials while keeping the device used as simple as
possible and, specifically, keeping the number of radiation sources
as low as possible.
[0005] A further object is to provide a device for executing a
method of this invention.
[0006] The first object is accomplished with the features of claim
1, the second object is achieved with the features of claim 13.
[0007] Conventional computer tomographs use x-ray sources moving
around the object and corresponding detectors, in order to create a
multitude of images from which the object is reconstructed
three-dimensionally with good resolution. With less than 10 views,
which are produced with an equivalent number of stationary
radiation sources, a complex object is incomplete, because of
mathematical reasons, and cannot be reconstructed with sufficient
resolution. Therefore, the method of this invention extracts
partial information from particular regions, which are selected
from individual views and are analyzed further. In the evaluation,
to begin with, a spatial geometric value in the area to be examined
is determined from positional data data of a 2-dimensional picture
and from intensity values using a predetermined value of a
specific, absorption-influenced value of a suspected material. In
addition, the corresponding spatial-geometric value is calculated
solely from 3-dimensional geometric values, which are determined
from measured intensity values. Next, the values from both
evaluations are directly or indirectly compared with one another,
in order to determine whether or not the suspected material is
indeed present.
[0008] The dependent claims contain preferred and especially
further advantageous variations of the method of this
invention:
[0009] The method of claim 2 compares both values of the
spatial-geometric value indirectly with one another, whereby the
value of a specific material is calculated and is subsequently
compared with a predetermined value.
[0010] In the method of claim 3, the volume of the material in the
region is determined from the area and the absorption thickness of
the region. In order to calculate the absorption thickness from the
measured intensity values, the predetermined value of the specific,
absorption-influenced value of a suspected material, especially the
predetermined density .phi. and/or the predetermined mass
attenuation coefficient .mu./.phi. is utilized. In a second
evaluation, the volume of the material in a region is estimated
using spatial positional data only. In a comparison, the values of
the volumes or the values derived from a calculated volume value
are compared with one another.
[0011] Claim 6 is for an especially advantageous method with an
indirect comparison based on claim 3. Mass is determined by
multiplying the volume, calculated from the area and the absorption
thickness, with the stored density of a suspected material. The
mass thus calculated is subsequently divided by the volume, which
was derived solely from spatial positional data. The such
calculated density value is compared with a stored density
value.
[0012] A preferred method for approximation of the volume is to
calculate the volume of a polyhedron encircling the region or
located in the region to be examined (claim 7).
[0013] In the method of claim 8, the absorption thickness
corresponding to the position of a 2-dimensional picture is
determined by using a stored value of absorption-influenced value,
especially the density .phi. and/or the mass attenuation
coefficient .mu./.phi.. To verify the evaluation results, the
corresponding thickness is determined solely from spatial
positional data.
[0014] In the particularly beneficial method of claim 11, the
object is radiated in at least three separate beam planes, of which
at least two are not parallel to one another. With only a few
2-dimensional pictures of the object, the to be examined spatial
region can be better defined when the images are as independent
from each other as possible, in other words, when they are not
solely derived from parallel beam planes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The drawing illustrates the invention showing a schematic
embodiment of a luggage inspection device:
[0016] FIG. 1 shows the principal layout of the device;
[0017] FIG. 2 is a front view of a device, which x-rays the object
in three beam planes;
[0018] FIG. 3 is a side view that illustrates the array of the
radiation sources and detectors of the device of FIG. 2;
[0019] FIG. 4 is the front view of a preferred embodiment, whereby
the object is radiated in five beam planes; and
[0020] FIG. 5 is a side view of the array of the radiation sources
and detectors of the device of FIG. 4.
MEANS OF PERFORMING THE INVENTION
[0021] The inspection device illustrated in the figures is used for
security screening of objects 1, particularly pieces of luggage, as
done at airports, whereby the articles 2 located in the pieces of
luggage are screened for their security relevance.
[0022] Essential components of the device are stationary radiation
sources 3.1-3.3 and corresponding detectors 4.1-4.5, from which the
intensities of the non-absorbed beams are measured. The radiation
sources 3.1-3.3 are positioned in such a way that the objects 1 are
transilluminated in different directions to receive the greatest
possible independent data. For that purpose, the radiation sources
3.1-3.3 are positioned in the travel direction of the objects 1,
spaced one after the other and positioned on different sides of the
radiation tunnel 6, through which the objects 1 are transported on
a transport device, preferably a conveyor 7.
[0023] Beams are projected from at least three, preferably
fan-shaped, beam planes 5.1-5.5 for the radiation of an object 1,
each beam being aligned to a corresponding detector 4.1-4.5.
Preferably, an object 1 is radiated in three separate beam planes
5.1-5.5, of which at least two are not parallel to one another. In
the embodiment of FIG. 3, the beam planes 5.1, 5.3 are not parallel
to beam plane 5.2; in the embodiment of FIG. 5 beam planes 5.1,
5.4, 5.5 are parallel to one another, the other two beam planes
5.2, 5.3 are inclined against each other as well as against beam
planes 5.1, 5, 4, 5.5. At least one beam plane is preferably
perpendicular to the transport direction of the objects 1. It is
advantageous to produce two beam planes, which are inclined to one
another, by masking the corresponding beams from a sole radiation
source via a collimator 8. The detectors 4.1-4.5 each have
detectors with a linear array, preferably L-shaped, so that all the
beams passing through the object 1 are detected. The radiation
sources 3.1-3.3 supply x-rays in an energy range up to a maximum of
140 keV. The detectors 4.1-4.5 contain dual detectors, which
measure the intensities separately for high and low energies, for
the so-called dual-energy-method.
[0024] Furthermore, the system provides an evaluator with a
computer and a screen 9, which displays the generated pictures of
the objects 1 and the articles 2 found therein, for additional
visual inspection by an operator. In the computer, besides the
evaluation software, there are stored values of at least one
specific, absorption-influenced value of different materials, the
presence of which is to be detected. Such materials are especially
explosives, the presence of which is to be detected in the object
1.
[0025] In order to detect a particular material in an object 1, for
example, an explosive, it is transported on the conveyor belt 7
through the different beam planes 5.1-5.5, wherein the intensities
of the non-absorbed radiation beams are measured by the
corresponding detector 4.1-4.5. To begin with, an at least
two-dimensional picture of the object 1 is generated from the
measured intensity values and stored in the computer for future
processing. The picture is constructed of pixel values of a
material value, which are derived from the intensities of the
corresponding detectors. The preferred procedure is to determine
the value of the effective atomic number Z.sub.eff for each picture
point, which is ascertained by the known dual-energy method,
whereby both intensity values of the high and low energy spectrum
are utilized. The ascertained value can be displayed on the screen
9 as an assigned gray or color value.
[0026] Next, those areas in the picture are determined where the
value of the material value, in the example the value of Z.sub.eff,
are in an interesting area, for example, in the value range for
explosives. This area of the picture displays an image of a spatial
region and thus, an article 2 within the object 1, and is selected
out for further examination.
[0027] In the examination, at least one spatial-geometric value in
the area to be examined is determined from positional data of a
two-dimensional picture and from intensity values, using a stored
value of a specific, absorption-influenced value of a suspected
material. Preferably, the values of the density .phi. and/or the
mass attenuation coefficient .mu./.phi. of the materials to be
detected are stored and used. Additionally, the corresponding
spatial-geometric value is determined solely from three-dimensional
values, which are determined from the measured intensity values. To
determine the spatial-geometric values as accurately as possible,
in the preferred embodiments of FIGS. 4 and 5, five different
two-dimensional pictures are generated, from which the
corresponding three-dimensional values are calculated. Finally, the
two determined values of the spatial-geometric value or from values
derived from the value of the spatial-geometric value are directly
or indirectly compared with one another to determine if the
suspected material is actually present.
[0028] A preferred spatial-geometric value is the volume of the
material in the spatial area to be tested. The volume is determined
two different ways: in the first determination, the area of the
two-dimensional picture of the area to be examined is calculated
first. Next, the absorption thickness of the spatial area is
determined from the intensity values of the radiation that passed
through the area. In order to determine the absorption thickness, a
stored value of a specific, absorption-influenced value of a
suspected material is retrieved, in particular the density .phi.
and/or the mass attenuation coefficient .mu./.phi.. The result is
the volume of the material in the region as a product of the area
and the absorption thickness.
[0029] In an additional step, the approximate volume of the
material in the region is determined from spatial positional data,
which can be exclusively determined from the intensity values of at
least three detector arrays. In a preferred method, the volume of a
polyhedron is calculated, which is situated in the region or
encases the region, which are determined as intensity values when
transporting the object 1 through at least three beam planes.
[0030] To check if the suspected material is actually present, in a
variation, the values of the volumes or the values of the
calculated volume value are subsequently compared directly to one
another, which have been determined according to both methods.
Preferably, for comparing purposes, in both methods the mass of the
materials in the region to be examined is determined as the product
of the volume and the stored density. This has the benefit that in
step 1 a minimal mass can be determined, which is necessary for the
screening in the second step.
[0031] A preferred way of an indirect comparison of the volumes
resulting from the two methods is such that the volume value
calculated in step 1, using the absorption thickness, is multiplied
with the stored density value .phi. of the suspected material in
order to determine the mass of the material in the area to be
examined. From the mass thus determined, a density value is
determined by dividing the volume value ascertained solely from
positional data arrived at through the second method and is then
compared with a stored density value. This method, too, has the
benefit that in a first step a mass is calculated from which a
minimal value for the continuation of the examination process can
be ascertained.
[0032] In a case where the suspected material is present, the
comparison values coincide sufficiently exactly in both the direct
and the indirect method.
[0033] Alternatively to the determination of the volume, the
absorption thickness of the area can also be determined as a
geometric value, whereby the absorption thickness assigned to a
position in a two-dimensional picture using a stored value of the
specific, absorption-influenced value of a suspected material is
determined. Preferably, as in the previously described volume
determination, values of the density .phi. and/or the mass
attenuation coefficient .mu./.phi. of the materials to be detected
are stored. The absorption thickness is preferably calculated under
the assumption that the material in the area has a certain
density.
[0034] Furthermore, the absorption thickness assigned to this point
is determined solely from spatial positional data, which is
determined through a three-dimensional analysis of at least three
two-dimensional pictures from various beam planes 5.1-5.5. Finally,
the two both of the determined thicknesses, or values derived
therefrom, for example, the densities or the masses, are compared
with one another. If the suspected material is present, both values
are sufficiently exactly the same.
* * * * *